In recent years seats for cars and light trucks have been formed by molding a foam bun that will serve as the seat cushion, and then attaching a pre-stitched fabric cover to the foam bun. Often, the fabric cover is attached to the foam bun by insert molding touch fastener strips into the outer surface of the foam bun and attaching cooperating touch fastener strips to an inner surface of the fabric cover. Generally, the fastener strips are attached to the fabric cover along the seams where the cover is stitched together, and held in place by the seam stitching. The touch fastener strips allow the seat manufacturer to rapidly and semi-permanently attach the fabric cover to the foam bun by pulling the fabric cover over the foam bun and pressing the opposed touch fastener strips on the foam bun and fabric cover together.
The touch fastener strips on the foam bun are typically recessed in trenches, to allow the seams in the fabric cover to be indented below the surface of the seat cushion. Indenting the seams in this manner forms aesthetically appealing indented creases in the surface of the seat cushion upholstery for a tailored look. The trenches also accommodate the additional thickness of upholstery fabric that is created where the seam is stitched.
For example, a foam bun 10, shown in FIG. 1, includes a central, generally planar portion 12 and a pair of bolsters 14, 16 disposed on either side of the central portion 12. The central portion 12 and bolsters 14, 16 are separated by trenches 18 which define sweeping curves. Trenches 18 are located in the seat cushion at the point of change in curvature formed where the surface of bolsters 14, 16 on the side of seat cushion 10 intersect central portion 12.
As shown in FIG. 2, touch fastener strips 24 are bonded to the bottom surface 17 of trenches 18, e.g., by insert molding the foam bun 10 onto the touch fastener strips 24 with hook elements 25 exposed for engagement with cooperative fastener strips 27 that are sewn to the fabric cover 29 along seams 31. Because the trenches 18 are indented below the surface 33 of the central portion 12, when the cooperative touch fastener strips 27 are pressed against the touch fastener strips 24 the double thickness of fabric 35 that is below seam 31 will be recessed in the trenches, resulting in a smooth outer surface at the seam area of the seat cover.
This attachment method works well for fabric covers having straight seams. However, if the fabric cover has seams that define sweeping curves, e.g., seams that have a curvature similar to that of trenches 18 in FIG. 1, problems occur because as the touch fastener strip extends around the curve in the trench the strip will tend to buckle. Seat designs having curved seams have become increasingly popular in the automotive industry, and thus attempts have been made to address this problem. Some manufacturers have cut and pieced together short sections of straight touch fastener strips. Other manufacturers have cut out curved sections from wider strips of touch fastener material. Both methods may result in an inefficient, time consuming process, waste material, and undesirably high production costs.
Alternately, touch fastener strips have been custom molded to accommodate the shape of a curved trench. This alternate solution results in custom-molded touch fastener strips that can only be used for trenches with a particular degree of curvature, increasing the cost of production and requiring the seat manufacturer to inventory a variety of different custom-molded touch fastener strips for trenches having different degrees of curvature.